A motor for use in an electric-drive vehicle such as an all-electric car and a hybrid car is driven at high rotation speed—the number of revolutions of 10000 r/min or more—and hence in the case where a permanent magnet is used in a rotor, a permanent magnet motor of interior permanent magnet type in which a magnet can be retained against centrifugal force resistance has been suggested (PTL 1 to PTL 3). A magnet including neodymium as a main component is used as a permanent magnet for use in an electric-drive vehicle, and heat generation in the magnet during high speed rotation can be a disadvantage.
Here, PTL 1 suggests a configuration in which magnets for a rotor are in a V-shaped arrangement, a flux barrier is provided on each side of the permanent magnet in the circumferential direction, and a gap is formed between the ends of the inner peripheral corners of the magnets, so that air is made to flow into the gaps between the magnets and the flux barriers in the axial direction to take away heat generated in the magnets and fins at axial ends are used for heat exchange.
PTL 2 discloses a configuration in which magnets for a rotor are in a V-shaped arrangement, and a ventilation passage for cooling is provided on an inner or outer peripheral side of the permanent magnet.
PTL 3 discloses a configuration in which magnets for a rotor are in a V-shaped arrangement, a flux barrier is provided at each of the circumferential both ends of the permanent magnets, gaps are provided on the inner peripheral side of the permanent magnets, a mold material for fixing a magnet is provided at the flux barrier and the gap, and a slit is provided at an inter-pole part, so that thermal stress at a bridge part between the slit and the flux barrier is alleviated.